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There is a thing called:

Brake specific fuel consumption (BSFC)

It's a figure to describe how much fuel an engine needs to produce X amounts of power.

http://www.land-and-sea.com/dyno-tech-talk/using_bsfc.htm

There is a calculator on this page ->

http://www.rceng.com/technical.aspx

My (standard) injectors are now at 85% duty cycle, I am making about 330HP at the crank. (running at AFR of 11.7)

The mixture was starting to lean out already, so I have ordered new injectors.

Edited by Torques
  • 2 weeks later...

From my personal experience the standard injectors can hold more than most think. As my 33 gtst is making 393hp@wheels on standard injectors...

For the dyno figure doubters it does 119mph down quarter..

Edited by fragz013

My (standard) injectors are now at 85% duty cycle, I am making about 330HP at the crank. (running at AFR of 11.7) The mixture was starting to lean out already, so I have ordered new injectors.

Hmmm if you are finding that the fuel flow into the engine is levelling off at 85% IDC I'd consider looking at whats supplying fuel to the injectors more than the injectors themselves, personally - what pump is that with?

almost 300 rwkw? doubtful

119mph isn't a bad trap speed though, to be fair... though in saying that when you are limited by small injectors you can still make a car quite a bit faster than many would expect doing sneaky wee tricks. At lower rpm you have a longer pulse period, so you can actually move more fuel with an equivalent duty cycle.

As an example - I've tuned a Silvia running a G4 Link & boost control but still on stock injectors was quite held back, hitting 85% at 7000rpm at the boost level we were setting it up for. That boost level just wasn't going to do the setup justice, so I set up a "tapering" boost curve which resulted in a boost level some 6-7psi higher at 4500rpm than at redline and progessively dropping down... but injector duty cycles still never went over 85%. The resulting change in how the car performs is VERY substantial, torque wins races and hp sells cars?

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